Brought in ballast, aggressive seaweed spreads along East Coast

LITTLETON, New Hampshire (Reuters) - An invasive Asian seaweed that likely was brought to the New England coast from Europe has spread across more than 400 miles of Atlantic coastline since it was first discovered in U.S. waters off Rhode Island in 2009, biologists say.

The Red Asian seaweed is creating problems for the fishing industry as it gums lobster traps and fishing pots while displacing marine creatures that feed on native seaweed varieties.

"It's outcompeting them," said Matt Bracken, a Northeastern University biologist who is studying the spread of the plant known scientifically as heterosiphonia japonica.

"It's better at taking up nutrients, it grows more readily and is not eaten as readily by animals like snails and small crustaceans," he said in an interview on Friday.

High school students in Maine recently collected Red Asian seaweed off the coast of Cape Elizabeth, near Portland, Maine, the farthest north it has yet been found. It has been sighted as far south as New York's Long Island. Some New England beaches have been blanketed with the seaweed, which emits a bad smell when it dries out.

Red seaweed is native to the waters around Japan and the Korean peninsula and scientists believe it arrived in Europe in the early 1980s, probably in France in a load of live baby oysters that were grown in aquaculture farms.

It has since spread as far south and east as Venice, Italy, on the Adriatic Sea and as far north as upper Scandinavia.

It likely spread from Europe to Rhode Island in the seawater used as ballast for cargo ships, scientists said.

Craig Schneider, who studies seaweed at Trinity College in Connecticut, first identified the red seaweed while walking the beach in Charlestown, Rhode Island in 2009. "I saw this plant and said, ‘I don't know this, I don't know what this is,'" he said.

"I brought it back to the lab and I knew in five seconds after looking under the microscope: oh no, this probably came from Europe."

The seaweed is likely to rapidly spread as far north as Newfoundland and as far south as North Carolina, Bracken said. In Norway researchers found that the seaweed, which clones itself asexually, extended its range up the coast by 500 miles in five years, he said.

Halting the red seaweed's spread in the ocean will be difficult. Bracken said sea urchins, which are voracious seaweed eaters, could help contain the species. However, sea urchin levels have declined sharply in the North Atlantic after fishermen began harvesting the species in recent years to sell urchins to Asian consumers, he said.